Cold-drawing pipes and tubes



June 20, 1.944. E N, SANDERS COLD-DRAWING PIPE AND TUBE Filed March 5,1941 ing adjacent to the inlet side of the die.

Patented June 20, 1944 COLD-DRAWING PIPES AND TUBES Elmer N. Sanders,Mount Lebanon, Pa., assigner to National Tube Company, a corporation ofNew Jersey Application March 5, 19'41, Serial No. 381,902

(Cl. 205--8l 2 Claims.

. to a water-bearing mixture of flour and tallow by dipping bundles ofthe tubing in tanks containing such compound. After this, the tubing waseither placed ondrying racks for sufficient time for most of thewater toevaporate, or the moisture was driven therefrom by running the tubingthrough a continuous drying oven. As is readily apparent, thefirst-mentioned drying method was very slow and the second quiteexpensive. In addition, the water in the compound caused an oxide toform on the pipe, necessitating pickling, and frequently resulted inlocalized corrosion or etch-pitting which seriously affected the qualityand appearance of the tubing and caused excessive rejections.

The present invention comprises a method of cold-drawing which iscalculated to overcome the foregoing difficulties in present-daymethods, which include slow and expensive lubricant drying periods,rusting or corrosion `causing extra pickling operations, andetch-pitting causing poor surface Aand many rejections.

According to the teachings of the present invention, the hot-rolledtubing is pickled (placed in an acid bath to remove the scale) and afterpassing through a neutralizing and washing bath is taken directly to thedraw-bench. Here the pickled and washed tubing is drawn through a dieand over an interiorly disposed mandrel to reduce the outer diameterand/or wall thickness. An oil base non-water-bearing lubricant isdirected onto the exterior and-interior of the tub-I The oil basenon-water-bearing lubricant gives the tubing a rust preventative coatingwhich prevents rusting should there be any appreciable delay before thetubing can be annealed.

After the drawing operation, the tubing is conventionally annealed (lowtemperature heat treatment which removes drawing strains and hardness).This is preferably done in an inert or reducing atmosphere to preventscaling, and accordingly no pickling is necessary in this method exceptthe initial pickling prior -to the first drawing. Ordinarily thehot-rolled tube must be drawn several times to attain the desireddiameter and wall thickness, and according to the present method theannealed tube can be immediately redrawn in theforegong manner and CIIannealed in sequence without intermediate pickling or other treatmentuntil the desired dimensions are obtained. By materially reducing thetime cycle for one drawing until the next drawing, there is obtained agreat saving in the cost of the finished tube.

Referring to the accompanying drawing, there is illustrated therein apreferred form of apparatus which may be employed for practicing themethod described hereinbefore.

More specifically:

Figure l is a side elevation of a part of the apparatus of the presentinvention;

Figure 2 is an enlarged fragmentary elevation, mostly in section, andillustrating those elements of the apparatus which are disposednteriorly of the tubular workpiece.

Referring more particularly to the drawing, the numeral I generallydesignates a drawbench of a type widely used in the cold-drawing ofmetallic pipes and tubes` and adjacent one end of which there isdisposed the usual drawing die 2.

According to the teachings of the present invention there is providedadjacent the drawing die 2, and on the entry side thereof, a spray ring3 which receives lubricant under pressure in a manner which will be morefully described hereinafter and ejects the same around the periphvery ofthe workpiece.

Disposed within the pipe or tube to be colddrawn, which is designatedhereinafter at X, is a hollow mandrel bar 4 carrying on its forward enda mandrel 5 having an enlarged .cylindrical head l for disposalimmediately opposite the working surfaces of the drawing die 2. As shownat 8 in Figure 2, the forward end of the enlarged cylindrical head l ofthe mandrel is relieved 'or beveled.

The extreme forward end of the hollow mandrel bar 4 and the extremerearward end of the mandrel 5 are of substantially the same diameter andare center bored and screw threaded as shown at II to accommodatebetween them a threaded stud I2 whereby the mandrel is rigidly securedto the hollow mandrel bar, thus permitting easy replacement of themandrel with its enlarged cylindrical head l when such is desired.

The rearward end of the hollow mandrel bar 4 carries an integral collarI4 which by means of nuts I6 and Il is secured to the forward endv thecentral bore 27 and extend forwardly and4 convergently with respect tothe mandrel 5 for the purpose of supplying lubricant to the exterior ofthe latter.

Due to the foregoing construction and arr-angement, the hollow mandrelbar il may be quickly replaced when necessary without disturbing thepiping connection afforded by the iitting 2| and flexible tube 23.

Referring more particularly to Figure l, beneath the draw-bench I andthe drawing die 2 there is disposed a sump '3G for the reception oflubricant stripped from the tube by the drawing die 2 and the hollowmandrel bar l5.. This sump 3l) has disposed thereabove a pair of slopingtrough plates 3| and 32 which extend in both directions along the drawbench i, as shown at 33 and 34 respectively, to provide receivingsurfaces for the lubricant; thus the lubricant is collected from boththe front and back of the drawing die 2. A pressure pump 35 is connectedwith the sump 30 by means of a suction line 3l and has connectedtherewith a piping system 38 which delivers lubricant to the flexiblehose 23 referred to hereinbefore and also the spray ring 3 which isdisposed around the aperture of the drawing die 2. Disposed inlthepiping system 33 is a pressure relief valve l which permits eX- cesslubricant to return to the sump 30, whereby there is maintained auniform pressure in the lubricating system. Control valves are providedas indicated at 44 and 45, to permit the separate regulation of supplyof lubricant to both the flexible hose 23 and the cylindrical ring 5.

The operation of drawing a tube is as follows:

The valves 44 and 45 are closed or throttled down to permit only a smallflow' of lubricant. The hollow mandrel bar d is pushed back axiallyabout two feet to clear the drawing die 21, and the end of the mandrel 5is moved either vertically or horizontally away from the pass line and atube is threaded over the Amandrel and mandrel bar until the pointed orreduced end reaches the mandrel. Enough lubricant is admitted to themandrel to assure its having flooded the inside of the tube past themandrel, which is always somewhat smaller than the inside of the undrawntube. The'tube and mandrel are then pushed back into the pass line andmoved axially until the point extends through the die. The valves 41%and 635 are then opened and lubricant floods both the outside and insidesurfaces of the tube near the die and mandrel. A plyer 5u grips thepointed end of the tube extending through the die and the tube is drawnthrough the die and over the mandrel.

It will be noted that as the tube is drawn down tight on the mandrel 5,no excess lubricant will pass the mandrel or through the die, during thedrawing operation. Just before the tube is completely drawn, the valvesMl and d5 are closed, thus stopping or reducing the flow of lubricantuntil the next tube is ready for its passage through the die.

While I have shown and described certain specic embodiments of myinvention, I do not intend to be specically limited thereto, since manydepartures may be made from the embodiments disclosed herein withoutdeparting from the spirit of the invention or the scope of the appendedlclaims.

I claim: l. The method of producing cold-drawn tubing, which comprisesproviding a hot-rolled pickled tube which has been subjected to aneutralizing washing operation, then immediately after the washingoperation transferring the tube directly to a draw-bench and therepassing it through a die and over a mandrel disposed interiorly of saiddie and tube, applying a liquid non-water-bearing lubricantsimultaneously to both the interior and the exterior surfaces of saidtube as it is being drawn through said die and prior to their passagetherethrough.

2. The method of producing cold-dravm tubv ing, which comprisesproviding a hot-rolled pick- ELMER N. SANDERS.

